Nonvolatile semiconductor memory device and method for manufacturing same

ABSTRACT

A nonvolatile semiconductor memory device, includes: a stacked structural unit including a plurality of insulating films alternately stacked with a plurality of electrode films in a first direction; a selection gate electrode stacked on the stacked structural unit in the first direction; an insulating layer stacked on the selection gate electrode in the first direction; a first semiconductor pillar piercing the stacked structural unit, the selection gate electrode, and the insulating layer in the first direction, a first cross section of the first semiconductor pillar having an annular configuration, the first cross section being cut in a plane orthogonal to the first direction; a first core unit buried in an inner side of the first semiconductor pillar, the first core unit being recessed from an upper face of the insulating layer; and a first conducting layer of the first semiconductor pillar provided on the first core unit to contact the first core unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 15/064,270, filedMar. 8, 2016, which is a continuation of and claims the benefit ofpriority under 35 U.S.C. §120 from U.S. Ser. No. 14/833,827, filed Aug.24, 2015 which is a continuation of U.S. Ser. No. 14/150,504, filed Jan.8, 2014, which is a continuation of U.S. Ser. No. 12/724,713, filed Mar.16, 2010, now U.S. Pat. No. 8,653,582, and is based upon and claims thebenefit of priority from prior Japanese Patent Application No.2009-072950, filed on Mar. 24, 2009, the entire contents of each ofwhich are incorporated herein by reference.

BACKGROUND

Field

Embodiments of the invention relate generally to a nonvolatilesemiconductor memory device and a method for manufacturing the same.

Background Art

Structures, for example, in which one-time programmable elements aredisposed between multiple layer interconnects, and structures in whichconventional NAND flash memory is formed in multiple layers by repeatedepitaxial formation of silicon films, etc., have been proposed astechnology to realize higher memory density without depending on thedownscaling of lithography. However, in such methods, the number oflithography steps undesirably increases as the number of stacksincreases.

To replace such technology, stacked vertical memory has been proposed(for example, refer to JP-A 2007-266143 (Kokai). In such technology, amemory string made of stacked memory elements is made with one formingby stacking any number of layers of stacked electrodes, collectivelymaking through-holes, forming a memory film including a charge storagelayer and the like on the inner walls of the through-holes, andsubsequently filling a polysilicon film into the interior. Thereby, amemory can be realized in which the number of lithography stepssubstantially does not increase even when the number of stacksincreases.

Technology also exists to make the semiconductor pillar forming thememory string in a hollow cylindrical configuration to improve thecharacteristics of the polysilicon channel transistor of such a stackedvertical memory. Thereby, the semiconductor pillar can be formed in athin film, the effect of states in the polysilicon film can be reduced,and the fluctuation of characteristics of memory cells can be reduced.

However, it is necessary to set the impurity concentration of thesource-drain diffusion layer and the channel portion to be relativelyhigh in the case where the semiconductor pillar has a hollow cylindricalconfiguration with a thin film and a reduced volume. To this end,performing ion implantation from the surface of the stacked structuralunit at high acceleration and high currents leads to problems such aslonger processing time, increased manufacturing costs, and poor positioncontrollability at deep positions of the stacked structural unit.

Thus, a structure of a high-concentration source-drain diffusion layerhaving high position controllability while using a hollow cylindricalsemiconductor pillar is desired.

SUMMARY

According to an aspect of the invention, there is provided a nonvolatilesemiconductor memory device, including: a stacked structural unitincluding a plurality of insulating films alternately stacked with aplurality of electrode films in a first direction; a selection gateelectrode stacked on the stacked structural unit in the first direction;an insulating layer stacked on the selection gate electrode in the firstdirection; a first semiconductor pillar piercing the stacked structuralunit, the selection gate electrode, and the insulating layer in thefirst direction, a first cross section of the first semiconductor pillarhaving an annular configuration, the first cross section being cut in aplane orthogonal to the first direction; a first core unit buried in aninner side of the first semiconductor pillar, the first core unit beingrecessed from an upper face of the insulating layer; and a firstconducting layer of the first semiconductor pillar provided on the firstcore unit to contact the first core unit.

According to another aspect of the invention, there is provided a methodfor manufacturing a nonvolatile semiconductor memory device, including:forming a stacked structural unit including an insulating filmalternately stacked with an electrode film on a major surface of asubstrate; forming a selection gate electrode on the stacked structuralunit; forming an insulating layer on the selection gate electrode;making a first through-hole piercing at least the selection gateelectrode and the insulating layer in a first direction perpendicular tothe major surface and forming a semiconductor film on an inner side faceof the first through-hole; forming a core unit on an inner side of thesemiconductor film; recessing the core unit; and introducing an impurityinto the semiconductor film.

According to another aspect of the invention, there is provided a methodfor manufacturing a nonvolatile semiconductor memory device, including:forming a stacked structural unit including an insulating filmalternately stacked with an electrode film on a major surface of asubstrate; forming a selection gate electrode on the stacked structuralunit; forming an insulating layer on the selection gate electrode;making a second through-hole and a third through-hole, the secondthrough-hole piercing the selection gate electrode in a first directionperpendicular to the major surface, the third through-hole piercing theinsulating layer in the first direction to communicate with the secondthrough-hole, a diameter of the third through-hole at an upper end ofthe insulating layer being larger than a diameter of the secondthrough-hole; forming a semiconductor film on inner side faces of thesecond through-hole and the third through-hole; and implanting animpurity into a portion of the semiconductor film on the selection gateelectrode side.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic cross-sectional views illustrating theconfiguration of a nonvolatile semiconductor memory device according toa first embodiment of the invention;

FIG. 2 is a schematic perspective view illustrating the configuration ofthe nonvolatile semiconductor memory device according to the firstembodiment of the invention;

FIGS. 3A to 3D are schematic cross-sectional views in order of theprocesses, illustrating the method for manufacturing the nonvolatilesemiconductor memory device according to the first example of theinvention;

FIGS. 4A to 4C are schematic cross-sectional views in order of theprocesses, continuing from FIG. 3D;

FIGS. 5A to 5C are schematic cross-sectional views illustrating theconfiguration of a nonvolatile semiconductor memory device and a methodfor manufacturing the same according to a second example of theinvention;

FIGS. 6A to 6D are schematic cross-sectional views illustrating theconfiguration of a nonvolatile semiconductor memory device and a methodfor manufacturing the same according to a third example of theinvention;

FIGS. 7A to 7C are schematic cross-sectional views in order of theprocesses, continuing from FIG. 6D;

FIGS. 8A to 8D are schematic cross-sectional views illustrating theconfiguration of a nonvolatile semiconductor memory device and a methodfor manufacturing the same according to a fourth example of theinvention;

FIGS. 9A to 9C are schematic cross-sectional views illustrating theconfiguration of a nonvolatile semiconductor memory device and a methodfor manufacturing the same according to a fifth example of theinvention;

FIGS. 10A to 10C are schematic cross-sectional views in order of theprocesses, continuing from FIG. 9C;

FIG. 11 is a schematic cross-sectional view illustrating theconfiguration of a nonvolatile semiconductor memory device according toa sixth example of the invention;

FIG. 12 is a schematic perspective view illustrating the configurationof another nonvolatile semiconductor memory device according to thefirst embodiment of the invention;

FIG. 13 is a flowchart illustrating a method for manufacturing anonvolatile semiconductor memory device according to a second embodimentof the invention; and

FIG. 14 is a flowchart illustrating another method for manufacturing thenonvolatile semiconductor memory device according to the secondembodiment of the invention.

DETAILED DESCRIPTION

Embodiments of the invention will now be described with reference to thedrawings.

The drawings are schematic or conceptual; and the relationships betweenthe thickness and width of portions, the proportional coefficients ofsizes among portions, etc., are not necessarily the same as the actualvalues thereof. Further, the dimensions and proportional coefficientsmay be illustrated differently among drawings, even for identicalportions.

In the specification of the application and the drawings, componentssimilar to those described in regard to a drawing thereinabove aremarked with like reference numerals, and a detailed description isomitted as appropriate.

First Embodiment

FIGS. 1A and 1B are schematic cross-sectional views illustrating theconfiguration of a nonvolatile semiconductor memory device according toa first embodiment of the invention.

FIG. 2 is a schematic perspective view illustrating the configuration ofthe nonvolatile semiconductor memory device according to the firstembodiment of the invention.

For easier viewing of the drawing, FIG. 2 illustrates only electricallyconducting portions, and insulating portions are omitted.

First, one example of the overview of the configuration of thenonvolatile semiconductor memory device according to this embodiment isdescribed using FIG. 2.

A nonvolatile semiconductor memory device 110 according to thisembodiment is a three dimensional stacked flash memory. As describedbelow, cell transistors are arranged in a three dimensional matrixconfiguration in the nonvolatile semiconductor memory device 110. Acharge storage layer is provided in each of the cell transistors. Eachof the cell transistors functions as a memory cell to store data bystoring a charge in the charge storage layer.

As illustrated in FIG. 2, a substrate 11 made of, for example, asemiconductor such as monocrystalline silicon and the like is providedin the nonvolatile semiconductor memory device 110. A memory arrayregion where memory cells are formed and a circuit region that drivesthe memory cells are set in the substrate 11. FIG. 2 illustrates theconfiguration of the memory array region, and the circuit region isomitted.

In the memory array region, a stacked structural unit ML is formed on amajor surface 11 a of the substrate 11. Electrode films WL arealternately stacked with insulating films 14 in the stacked structuralunit ML.

An XYZ orthogonal coordinate system will now be introduced forconvenience of description in the specification of the application. Inthis coordinate system, a direction perpendicular to the major surface11 a of the substrate 11 is taken as a Z-axis direction (firstdirection). One direction in a plane parallel to the major surface 11 ais taken as an X-axis direction (second direction). A directionperpendicular to the Z axis and the X axis is taken as a Y-axisdirection (third direction).

Namely, the stacking direction of the electrode films WL and theinsulating films 14 in the stacked structural unit ML is the Z-axisdirection.

Semiconductor pillars SP piercing the stacked structural unit ML in theZ-axis direction are provided.

Selection gate electrodes SG are provided above the stacked structuralunit ML. Any conducting material may be used as the selection gateelectrodes SG; and polysilicon, for example, may be used. The selectiongate electrodes SG are formed by dividing a conducting film along acertain direction. In this specific example, the selection gateelectrodes SG are divided along the Y-axis direction. In other words,the selection gate electrodes SG are multiple conducting members havinginterconnect configurations aligned in the X-axis direction.

On the other hand, the electrode films WL are conducting films parallelto the XY plane and divided, for example, into erasing block units. Theelectrode films WL also may be divided to align, for example, in theX-axis direction similarly to the selection gate electrodes SG.

Multiple through-holes TH are made in the stacked structural unit ML andthe selection gate electrodes SG to align in the stacking direction (theZ-axis direction). The semiconductor pillars SP are formed by providingan insulating film on the side faces of the interiors of thethrough-holes TH and filling a semiconductor material into the space onthe inner sides thereof.

The semiconductor pillar SP is multiply provided in the XY plane. Inthis specific example, two semiconductor pillars SP arranged adjacentlyin the Y-axis direction form one pair. In other words, the nonvolatilesemiconductor memory device 110 further includes a first connectionportion CP1 (connection portion CP) that electrically connects a firstsemiconductor pillar SP1 and a second semiconductor pillar SP2 on thesubstrate 11 side. Namely, the first and second semiconductor pillarsSP1 and SP2 are connected by the first connection portion CP1 andfunction as one NAND string having a U-shaped configuration. Third andfourth semiconductor pillars SP3 and SP4 are provided adjacent to thesecond semiconductor pillar SP2 in the Y-axis direction on the sideopposite to the first semiconductor pillar SP1, are connected to eachother by a second connection portion CP2, and function as another NANDstring having a U-shaped configuration. Thus, two semiconductor pillarSP pairs are formed.

Then, for example, the two adjacent semiconductor pillars (thesemiconductor pillars SP2 and SP3) on the inner side of the two NANDstrings having the U-shaped configurations are connected to a sourceline SL. The two semiconductor pillars (the semiconductor pillars SP1and SP4) on the outer sides are connected to the same bit line BL bythrough-electrodes V1 and V2, respectively.

Thus, in a stacked vertical memory, a polysilicon contact is unnecessaryat the lower portion of the memory string because the memory strings areconnected in a U-shaped configuration, and the degrees of freedom of thememory film configuration increase.

In other words, in a stacked vertical memory, it is necessary to formthe gate insulating film of the memory element prior to forming thepolysilicon film forming the channel. At this time, it is necessary toobtain a good polysilicon-polysilicon contact at the lower portion ofthe semiconductor pillar SP because a current flows in the memorystring. It is necessary to use, for example, a memory film configurationthat can withstand dilute hydrofluoric acid processing, and there areconstraints on the memory film configuration. Conversely, as describedabove, a memory string having a U-shaped configuration can resolve suchconstraints and is advantageous, for example, in the case wheremulti-bit technology and the like are promoted as methods to furtherincrease the density of the stacked vertical memory recited above, etc.

However, as described below, the invention is not limited thereto. Eachof the semiconductor pillars SP may be independent. In such a case, thesemiconductor pillars SP are not connected by the connection portion CP,and selection gate electrodes are provided at both the upper portion andthe lower portion of the stacked structural unit ML to select thesemiconductor pillars SP. Hereinbelow, the case is described where twoof the semiconductor pillars SP are connected by the connection portionCP.

Herein, “semiconductor pillar SP” is used to refer to all of thesemiconductor pillars or any semiconductor pillar; and “semiconductorpillar SPN” (N being any integer not less than 1) is used to refer to adesignated semiconductor pillar.

The electrode films corresponding to the semiconductor pillars SP1 andSP4 are commonly connected, and the electrode films corresponding to thesemiconductor pillars SP2 and SP3 are commonly connected. Similarly, theelectrode films corresponding to the semiconductor pillars SP(4M+1) andSP(4M+4) are commonly connected, where M is an integer not less than 0and the N recited above is (4M+1) and (4M+4); and the electrode filmscorresponding to the semiconductor pillars SP(4M+2) and (4M+3) arecommonly connected, where N is (4M+2) and (4M+3).

In other words, the electrode films WL have an inter digital electrodeor multi-finger electrode structure in which the electrode films WL arecombined with each other in a comb teeth configuration opposing in theX-axis direction.

The electrode films WL corresponding to the semiconductor pillarsSP(4M+1) and SP(4M+4) and the electrode films WL corresponding to thesemiconductor pillars SP(4M+2) and (4M+3) are electrically connected atboth ends in the X-axis direction to, for example, the peripheralcircuit provided in the substrate 11. In other words, similarly to, forexample, the stairstep structure discussed in JP-A 2007-266143 (Kokai),the length in the X-axis direction of each of the electrode films WLstacked in the Z-axis direction changes in a stairstep configuration;and each of the electrode films WL is connected to the peripheralcircuit at each of the ends in the X-axis direction.

Thereby, the memory cells of the same layer corresponding to the firstsemiconductor pillar SP1 and the second semiconductor pillar SP2 can beoperated independently from each other; and the memory cells of the samelayer corresponding to the third semiconductor pillar SP3 and the fourthsemiconductor pillar SP4 can be operated independently from each other.

The combination of the electrode films corresponding to thesemiconductor pillars SP(4M+1) and SP(4M+4) and the electrode filmscorresponding to the semiconductor pillars SP(4M+2) and (4M+3) can betaken to be one erasing block; and each of the electrode films can bedivided for each erasing block.

The number of the semiconductor pillars included in each of the erasingblocks in the X-axis direction and the Y-axis direction is arbitrary.

FIGS. 1A and 1B illustrate the configuration of a portion of thenonvolatile semiconductor memory device 110. Namely, FIG. 1A illustratesthe semiconductor pillar SP1 illustrated in FIG. 2, and FIG. 1Billustrates a further enlarged portion corresponding to the stackedstructural unit ML of the semiconductor pillar SP1.

As illustrated in FIGS. 1A and 1B, an inter-layer insulating film 11 bis provided on the major surface 11 a of the substrate 11. The back gateBG is provided thereupon, and the stacked structural unit ML is providedthereupon. In the stacked structural unit ML, multiple insulating films14 are alternately stacked with multiple electrode films WL in theZ-axis direction (the first direction).

The selection gate electrode SG is provided on the stacked structuralunit ML in the Z-axis direction. The insulating layer 16 is provided onthe selection gate electrode SG in the Z-axis direction.

The semiconductor pillar SP piercing the stacked structural unit ML, theselection gate electrode SG, and the insulating layer 16 in the Z-axisdirection is provided. The cross section (the first cross section) ofthe semiconductor pillar SP has an annular configuration when cut in aplane orthogonal to the Z-axis. In other words, the semiconductor pillarSP has a hollow cylindrical configuration.

A core unit 68 is buried in the inner side of the semiconductor pillarSP. The upper end of the core unit 68 is recessed below the upper end ofthe insulating layer 16. In other words, the core unit 68 is recessedfrom the upper face of the insulating layer 16.

A first conducting layer 18 is provided on the core unit 68 (in theZ-axis direction) on the inner side of the semiconductor pillar SP.

The invention is not limited thereto. As described below, it issufficient that the first conducting layer 18 is provided on the coreunit 68 on the inner side of the semiconductor pillar SP, on thesemiconductor pillar SP, or both.

A configuration similar to that of the first semiconductor pillar SP1 isprovided also for the second semiconductor pillar SP2 described above.In other words, the nonvolatile semiconductor memory device 110includes: the stacked structural unit ML including the multipleinsulating films 14 alternately stacked with the multiple electrodefilms WL in the first direction; the selection gate electrode SG stackedon the stacked structural unit ML in the first direction; the insulatinglayer 16 stacked on the selection gate electrode SG in the firstdirection; and the first semiconductor pillar SP1 piercing the stackedstructural unit ML, the selection gate electrode SG, and the insulatinglayer 16 in the first direction. A cross section (a first cross section)of the first semiconductor pillar SP1 has an annular configuration whencut in a plane orthogonal to the first direction. A first core unit isburied in an inner side of the first semiconductor pillar SP1 and isrecessed from the upper face of the insulating layer 16. The firstconducting layer of the first semiconductor pillar SP1 is provided onthe first core unit to contact the first core unit.

The nonvolatile semiconductor memory device 110 further includes: thesecond semiconductor pillar SP2 adjacent to the first semiconductorpillar SP1 in the second direction (in this case, the Y-axis direction)orthogonal to the first direction (the Z-axis direction), where thesecond semiconductor pillar SP2 pierces the stacked structural unit ML,the selection gate electrode SG, and the insulating layer 16 in thefirst direction, and a cross section (a second cross section) of thesecond semiconductor pillar SP2 has an annular configuration when cut ina plane orthogonal to the first direction; the second core unit buriedin the inner side of the second semiconductor pillar SP2, where thesecond core unit is recessed from the upper face of the insulating layer16; the first conducting layer of the second semiconductor pillar SP2provided on the second core unit to contact the second core unit; andthe connection portion CP connecting the first semiconductor pillar SP1and the second semiconductor pillar SP2 on a side opposite to theinsulating layer 16.

Hereinbelow, the first semiconductor pillar SP1 and the secondsemiconductor pillar SP2 are referred to as the semiconductor pillar SP.The first core unit and the second core unit are referred to as the coreunit 68. The first conducting layer of the first semiconductor pillarSP1 and the first conducting layer of the second semiconductor pillarSP2 are referred to as the first conducting layer 18.

Any insulating material may be used as the insulating layer 16. Forexample, SiO₂ may be used. Any semiconductor material may be used as thesemiconductor pillar SP. For example, polysilicon, amorphous silicon,etc., may be used. Any insulating material may be used as the core unit68. For example, SiN may be used. Any conducting material may be used asthe first conducting layer 18. For example, polysilicon including anadded impurity may be used.

As illustrated in FIG. 1B, a memory unit stacked film 61 is providedbetween the semiconductor pillar SP and the electrode film WL. Thememory unit stacked film 61 includes a charge storage layer 63 providedbetween the semiconductor pillar SP and the electrode films WL, a firstmemory unit insulating film 61 a provided between the electrode films WLand the charge storage layer 63, and a second memory unit insulatingfilm 61 b provided between the semiconductor pillar SP and the chargestorage layer 63.

In other words, the through-hole TH is provided to pierce the stackedstructural unit ML in the Z-axis direction; the memory unit stacked film61 made of the stacked films of the second memory unit insulating film61 b, the charge storage layer 63, and the first memory unit insulatingfilm 61 a is provided on the inner wall of the through-hole TH; and thesemiconductor pillar SP having the hollow cylindrical configuration isprovided on the side face of the inner side of the memory unit stackedfilm 61.

However, the nonvolatile semiconductor memory device for which thisembodiment is applied is not limited to that recited above. It issufficient to use a structure in which the semiconductor pillar isprovided to pierce the stacked structural unit ML in the stackingdirection, where the stacked structural unit ML includes the electrodefilms WL alternately stacked with the insulating films 14. The structureof the memory unit stacked film 61 recited above is arbitrary. Forexample, at least a portion of at least one selected from the chargestorage layer 63, the first memory unit insulating film 61 a, and thesecond memory unit insulating film 61 b may be provided between theelectrode films WL.

Any conducting material may be used as the electrode film WL. Forexample, amorphous silicon or polysilicon provided with an electricalconductivity by introducing an impurity may be used. Metal, alloys,etc., also may be used. A prescribed potential is applied to theelectrode film WL by a driver circuit (not illustrated) formed in thecircuit region, and the electrode film WL functions as a word line ofthe nonvolatile semiconductor memory device 110.

On the other hand, silicon oxide, for example, may be used as theinsulating film 14, the first memory unit insulating film 61 a, and thesecond memory unit insulating film 61 b.

The insulating film 14 functions as an inter-layer insulating film toinsulate the electrode films WL from each other. The first memory unitinsulating film 61 a provided between the electrode films WL and thecharge storage layer 63 functions as a block insulating film. The secondmemory unit insulating film 61 b provided between the semiconductorpillar SP and the charge storage layer 63 functions as a tunnelinginsulating film.

A silicon nitride film, for example, may be used as the charge storagelayer 63. The charge storage layer 63 stores or emits a charge by anelectric field applied between the semiconductor pillar SP and theelectrode film WL such that the charge storage layer 63 functions as astorage layer. The charge storage layer 63 may be a single-layer film ora stacked film.

A region proximal to the portion where the semiconductor pillar SP facesthe electrode film WL forms one memory cell MC.

An example of the nonvolatile semiconductor memory device having such astructure will now be described.

First Example

As illustrated in FIGS. 1A and 1B, a nonvolatile semiconductor memorydevice 111 of a first example has the structure of the nonvolatilesemiconductor memory device 110 illustrated in FIGS. 1A and 1B.

The nonvolatile semiconductor memory device 111 uses p⁺ polysiliconhaving, for example, a thickness of 200 nm (nanometers) as the selectiongate electrode SG and a TEOS (Tetra Ethyl Ortho Silicate) film having,for example, a thickness of 300 nm as the insulating layer 16. A SiNfilm, for example, is used as the core unit 68. The upper end of thecore unit 68 is disposed above the selection gate electrode SG and belowthe upper end of the insulating layer 16 in the Z-axis direction. Asource-drain diffusion region SDR is provided in the semiconductorpillar SP at a position proximal to the upper end of the selection gateelectrode SG. The lower end of the source-drain diffusion region SDR ispositioned, for example, about 50 nm downward from the upper end of theselection gate electrode SG. A metal plug 21 is provided on the upperend of the semiconductor pillar SP and the upper end of the firstconducting layer 18. The metal plug 21 forms, for example, thethrough-electrode V1 illustrated in FIG. 2 or is electrically connectedto the through-electrode V1.

The nonvolatile semiconductor memory device 111 is manufactured, forexample, as follows.

FIGS. 3A to 3D are schematic cross-sectional views in order of thesteps, illustrating the method for manufacturing the nonvolatilesemiconductor memory device according to the first example of theinvention.

FIGS. 4A to 4C are schematic cross-sectional views in order of thesteps, continuing from FIG. 3D.

First, as illustrated in FIG. 3A, the inter-layer insulating film 11 band the back gate BG are formed on a substrate made of silicon. Thestacked structural unit ML including the insulating films 14 alternatelystacked with the electrode films WL is formed thereupon. A memorytransistor hole Hm is made in the stacked structural unit ML and aportion of the back gate BG to align in the Z-axis direction usinglithography and RIE. A sacrificial film SF made of, for example, a SiNfilm is filled into the interior of the memory transistor hole Hm. Thediameter of the memory transistor hole Hm is, for example, 60 nm.

The connection portion CP made of, for example, a SiN film is formedbeforehand in the back gate BG. The connection portion CP and thesacrificial film SF are connected to each other.

The inter-layer insulating film 15, a selection gate electrode film SGfforming the selection gate electrode SG of the selection transistor, andan extension inter-layer insulating film 16 f forming the insulatinglayer 16 are stacked on the stacked structural unit ML. The selectiongate electrode film SGf is formed of p⁺ polysilicon having, for example,a thickness of 200 nm. A TEOS film having, for example, a thickness of300 nm is used as the extension inter-layer insulating film 16 f.

Then, a selection transistor hole Hs is made by lithography and RIE topierce the extension inter-layer insulating film 16 f and the selectiongate electrode film SGf to reach the sacrificial film SF. As illustratedin FIG. 3B, the SiN film forming the sacrificial film SF and the SiNfilm forming the connection portion CP are removed in, for example, ahot phosphoric acid solution to connect the selection transistor holeHs, the memory transistor hole Hm, and the hole of the connectionportion CP to form a memory string hole Ht having a U-shapedconfiguration.

As illustrated in FIG. 3C, the first memory unit insulating film 61 amade of SiO₂, the charge storage layer 63 made of SiN, and the secondmemory unit insulating film 61 b made of SiO₂, for example, are stackedon the inner wall face of the memory string hole Ht to form the memoryunit stacked film 61.

Then, a semiconductor pillar film SPf forming the semiconductor pillarSP is deposited. A polycrystalline semiconductor film or an amorphoussemiconductor film (e.g., an amorphous silicon film of about 7 nm) maybe used as the semiconductor pillar film SPf. At this time, the memorystring hole Ht is not completely filled, and at least a portion of theinterior is left hollow.

Continuing as illustrated in FIG. 3D, annealing is performed, forexample, at 600° C. in an inert atmosphere (e.g., N₂) to increase thecrystallinity of the semiconductor pillar film SPf. Subsequently,annealing is performed again in an oxidation atmosphere to oxidize theside face of the inner side of the semiconductor pillar film SPf. Then,a core unit insulating film 68 f forming the core unit 68 is filled intothe interior. A SiN film, for example, may be used as the core unitinsulating film 68 f. Such a SiN film is formed by, for example, CVD(Chemical Vapor Deposition).

Then, as illustrated in FIG. 4A, the core unit insulating film 68 f isrecessed by performing etch-back with RIE such that an upper end 68 fuof the core unit insulating film 68 f is on the upper side (the sideopposite to the substrate 11) of an upper end SGfu of the selection gateelectrode film SGf. Specifically, a distance t1 between the upper end 68fu of the core unit insulating film 68 f and the upper end SGfu of theselection gate electrode film SGf in the Z-axis direction is about 100nm.

Continuing as illustrated in FIG. 4B, impurity implantation is performedon the semiconductor pillar film SPf. The conditions of the impurityimplantation may include, for example, phosphorus as the impurity, anacceleration energy of 60 KeV, and an impurity concentration of 1×10¹⁵cm⁻². At this time, the impurity implanted into the core unit insulatingfilm 68 f also recoils in the horizontal direction (the directionperpendicular to the Z-axis direction), and the source-drain diffusionregion SDR is formed by implanting the impurity into the semiconductorpillar film SPf.

In other words, the implanting (introducing) of the impurity includesirradiating the impurity on the recessed core unit 68 (the core unitinsulating film 68 f), causing a travel direction of the impurity tohave a component in a direction orthogonal to the first direction (theZ-axis direction), and introducing the impurity into the semiconductorfilm (the semiconductor pillar film SPf).

Then, as illustrated in FIG. 4C, pre-processing with a dilutehydrofluoric acid solution is performed. Subsequently, aphosphorus-doped polysilicon film 18 f forming the first conductinglayer 18 is filled onto the core unit insulating film 68 f in theselection transistor hole Hs. Subsequently, the polysilicon film (thesemiconductor pillar film SPf) on the extension inter-layer insulatingfilm 16 f is removed.

In other words, the first conducting layer 18 is formed to contact thecore unit (the core unit insulating film 68 f) by filling a conductingmaterial onto the semiconductor film (the semiconductor pillar film SPf)including the introduced impurity in the through-hole (the selectiontransistor hole Hs or the memory string hole Ht).

At this time, impurity implantation may be performed into thephosphorous-doped polysilicon film 18 f to make the contact with themetal plug 21 more reliably. In such a case, the conditions of theimpurity implantation may include, for example, an impurity of As, anacceleration energy of 40 KeV, and an impurity concentration of 1×10¹⁵cm⁻².

Further, annealing is performed, for example, in a N₂ atmosphere at 950°C. for about 10 seconds to activate the impurity.

Subsequently, the memory unit stacked film 61 on the extensioninter-layer insulating film 16 f is removed. Then, an inter-layerinsulating film 19 is deposited thereupon. A trench 20 is made in theinter-layer insulating film 19. Then, a metal film such as a stackedfilm of, for example, a W film 21 b or a TiN film 21 a is filled intothe trench 20 to form the metal plug 21.

Thus, the nonvolatile semiconductor memory device 111 illustrated inFIGS. 1A and 1B can be constructed.

The nonvolatile semiconductor memory device 111 provides effects such asthose recited below.

First, because the core unit insulating film 68 f is recessed such thatthe impurity implantation is performed in a state in which the upper end68 fu of the core unit insulating film 68 f is proximal to the selectiongate electrode SG, the acceleration energy during the impurityimplantation can be relatively low, and it is easy to increase thecurrent during the impurity implantation. In other words, a lowacceleration energy and a high current can be used. Thereby, the timenecessary for the step of impurity implantation can be reduced, andmanufacturing costs can be reduced.

Because the distance to the selection gate electrode SG during theimpurity implantation is reduced, the impurity can be implanted at ahigh concentration, and the controllability of the impurityconcentration in the Z-axis direction is high.

Thus, the nonvolatile semiconductor memory device 111 can be applied toa hollow cylindrical semiconductor pillar to realize ahigh-concentration source-drain diffusion layer having high positionalcontrollability at low manufacturing costs.

In the case where conventional methods are used with a semiconductorpillar SP having a thin hollow cylindrical configuration in which thethickness of the semiconductor pillar film SPf is several nanometers,voids and the like occur during a silicide reaction at the interfacewhen connecting the metal plug 21 to the semiconductor pillar film SPf,and open defects easily occur. However, such problems are solved by thenonvolatile semiconductor memory device 111. In other words, in thenonvolatile semiconductor memory device 111, the side face of thesemiconductor pillar film SPf (the semiconductor pillar SP) and the sideface of the phosphorous-doped polysilicon film 18 f (the firstconducting layer 18) contact each other with a large surface area evenin the case where the semiconductor pillar film SPf is thin, and thesemiconductor pillar SP can be stably electrically connected to thefirst conducting layer 18. The metal plug 21 contacts the semiconductorpillar SP and the first conducting layer 18 with the surface areacorresponding to the diameter of the memory string hole Ht. Also, suchcontact is a metal-polysilicon contact which easily provides stableconnection characteristics. Thereby, effects are provided that the opendefects recited above can be reduced and the yield improves.

Although ion implantation such as that recited above may be used in thestep described in regard to FIG. 4B, vapor phase diffusion of theimpurity, for example, also may be used. In other words, as illustratedin FIG. 4B, a SiN film having a high heat resistance is used as the coreunit insulating film 68 f when implanting the impurity into thesemiconductor pillar film SPf, and such a configuration can alsowithstand the high-temperature processing of vapor phase diffusion.

Second Example

FIGS. 5A to 5C are schematic cross-sectional views illustrating theconfiguration of a nonvolatile semiconductor memory device and a methodfor manufacturing the same according to a second example of theinvention.

Namely, FIG. 5A is a schematic cross-sectional view illustrating theconfiguration of the nonvolatile semiconductor memory device. FIGS. 5Band 5C are schematic cross-sectional views in order of the steps,illustrating the method for manufacturing the same.

In a nonvolatile semiconductor memory device 112 of the second exampleaccording to the first embodiment of the invention, the upper end of thecore unit 68 is disposed between the upper end and the lower end of theselection gate electrode SG on the upper end side of the selection gateelectrode SG as illustrated in FIG. 5A. The lower end of the firstconducting layer 18 faces the selection gate electrode SG.

Such a nonvolatile semiconductor memory device 112 may be manufactured,for example, as follows.

After implementing the processing illustrated in FIGS. 3A to 3D to fillthe core unit insulating film 68 f forming the core unit 68 into theinterior of the inner side of the semiconductor pillar film SPf,etch-back is performed on the core unit insulating film 68 f by, forexample, RIE as illustrated in FIG. 5B such that the upper end 68 fu ofthe core unit insulating film 68 f is recessed below (to the substrate11 side) of the upper end SGfu of the selection gate electrode film SGf.In this specific example, a distance t2 between the upper end 68 fu ofthe core unit insulating film 68 f and the upper end SGfu of theselection gate electrode film SGf in the Z-axis direction is, forexample, about 50 nm.

As illustrated in FIG. 5C, pre-processing in a dilute hydrofluoric acidsolution is performed. Subsequently, the phosphorous-doped polysiliconfilm 18 f is filled onto the core unit insulating film 68 f in theselection transistor hole Hs. Then, the polysilicon film (thesemiconductor pillar film SPf) on the extension inter-layer insulatingfilm 16 f is removed. In other words, in this manufacturing method, theimpurity implantation processing described in regard to FIG. 4B isomitted.

At this time, the impurity implantation may be performed into thephosphorous-doped polysilicon film 18 f to make the contact with themetal plug 21 more reliable. In such a case, the conditions of theimpurity implantation may include, for example, an impurity of As, anacceleration energy of 40 KeV, and an impurity concentration of 1×10¹⁵cm⁻².

Further, annealing is performed, for example, in a N₂ atmosphere at 950°C. for about 10 seconds to activate the impurity.

Thereafter, the inter-layer insulating film 19 and the metal plug 21 areformed similarly to those of the first example, and the nonvolatilesemiconductor memory device 112 illustrated in FIG. 5A can beconstructed.

The nonvolatile semiconductor memory device 112 provides effects such asthose recited below.

In the nonvolatile semiconductor memory device 111 according to thefirst example, the source-drain diffusion region SDR opposing to theselection gate electrode SG is formed by the impurity implantationdescribed in regard to FIG. 4B. Conversely, in the nonvolatilesemiconductor memory device 112 according to the second example, thesource-drain diffusion region SDR is formed by lowering thephosphorous-doped polysilicon film 18 f to a position opposing to theselection gate electrode SG. The impurity in the phosphorous-dopedpolysilicon film 18 f is introduced into the semiconductor pillar filmSPf at a prescribed concentration by, for example, diffusion duringactivation annealing. Thereby, the manufacturing steps of thesemiconductor device are reduced, and further cost reductions arepossible.

Third Example

FIGS. 6A to 6D are schematic cross-sectional views illustrating theconfiguration of a nonvolatile semiconductor memory device and a methodfor manufacturing the same according to a third example of theinvention.

Namely, FIG. 6A is a schematic cross-sectional view illustrating theconfiguration of the nonvolatile semiconductor memory device. FIGS. 6B,6C, and 6D are schematic cross-sectional views in order of the steps,illustrating the method for manufacturing the same. FIGS. 7A to 7C areschematic cross-sectional views in order of the steps, continuing fromFIG. 6D.

In a nonvolatile semiconductor memory device 113 of the third exampleaccording to the first embodiment of the invention illustrated in FIG.6A, a barrier insulating film 67 made of, for example, SiN is providedon the wall face of the inner side of the semiconductor pillar SP. Asecond conducting layer 70 is provided on the inner side of the barrierinsulating film 67.

In other words, in the nonvolatile semiconductor memory device 113, thecore unit 68 includes the barrier insulating film 67 provided on theside wall of the semiconductor pillar SP and the second conducting layer70 filled onto the inner side of the barrier insulating film 67 toelectrically connect to the first conducting layer 18. The same materialas the first conducting layer 18 may be used as the second conductinglayer 70.

In such a case, the depth of the connection portion CP is made shallowerthan those of the examples hereinabove, and the second conducting layer70 does not pass through the connection portion CP in the horizontaldirection. Thereby, the second conducting layer 70 is prevented fromcausing shorts between the bit line BL and the source line SL, andhighly reliable reading operations can be realized while using the samematerial as the first y conducting layer 18 to reduce steps.

Such a nonvolatile semiconductor memory device 113 may be manufactured,for example, as follows.

After implementing the processing illustrated in FIGS. 3A to 3C to formthe memory unit stacked film 61 and the semiconductor pillar film SPf onthe inner wall face of the memory string hole Ht, annealing is performedat, for example, 600° C. in an inert atmosphere (e.g., in N₂) toincrease the crystallinity of the semiconductor pillar film SPf asillustrated in FIG. 6B. Then, the side face of the inner side of thesemiconductor pillar film SPf is oxidized by annealing in an oxidationatmosphere; the barrier insulating film 67 is deposited on the wall faceof the inner side of the semiconductor pillar film SPf; and a coatedsacrificial film 69 is filled into the remaining space on the inner sideof the barrier insulating film 67.

A SiN film, for example, may be used as the barrier insulating film 67recited above. The thickness of the barrier insulating film 67 may be,for example, about 5 nm. At this time, the barrier insulating film 67does not completely fill the memory string hole Ht. In other words, thebarrier insulating film 67 does not completely fill the interior of thememory string hole Ht proximal to at least the selection gate electrodeSG. Thereby, the coated sacrificial film 69 recited above is formed onthe inner side of the barrier insulating film 67 in the interior of thememory string hole Ht. A photoresist, for example, may be used as thecoated sacrificial film 69.

Then, as illustrated in FIG. 6C, etch-back is performed on the coatedsacrificial film 69 by RIE such that an upper end 69 u of the coatedsacrificial film 69 of the interior of the memory string hole Ht isabove the upper end SGfu of the selection gate electrode film SGf. Adistance t3 from the upper end 69 u of the coated sacrificial film 69 tothe upper end SGfu of the selection gate electrode film SGf is about 100nm.

Continuing as illustrated in FIG. 6D, the barrier insulating film 67 ofthe upper portion of the memory string hole Ht (above the selection gateelectrode SG) is removed by CDE (chemical dry etching) based on, forexample, CF₄ gas.

Then, as illustrated in FIG. 7A, impurity implantation is performed onthe semiconductor pillar film SPf. The conditions of the impurityimplantation may include, for example, phosphorus as the impurity, anacceleration energy of 60 KeV, and an impurity concentration of 1×10¹⁵cm⁻². At this time, the impurity implanted into the coated sacrificialfilm 69 and the barrier insulating film 67 also recoils in thehorizontal direction (the direction perpendicular to the Z-axisdirection) and is implanted into the semiconductor pillar film SPf toform the source-drain diffusion region SDR.

Continuing as illustrated in FIG. 7B, the coated sacrificial film 69 isremoved by, for example, ashing and wet processing.

Then, as illustrated in FIG. 7C, pre-processing with a dilutehydrofluoric acid solution, for example, is performed. Subsequently, thephosphorus-doped polysilicon film 18 f is filled. At this time, thephosphorous-doped polysilicon film 18 f buried in the inner side of thebarrier insulating film 67 in the interior of the memory string hole Htforms the second conducting layer 70; and above the selection gateelectrode film SGf, the phosphorous-doped polysilicon film 18 f filledinto the space of the interior of the memory string hole Ht forms thefirst conducting layer 18. In other words, the same material may be usedas the second conducting layer 70 and the first conducting layer 18.

Subsequently, the polysilicon film (the semiconductor pillar film SPf)on the extension inter-layer insulating film 16 f is removed.

At this time, impurity implantation may be performed into thephosphorous-doped polysilicon film 18 f to make the contact with themetal plug more reliable. In such a case, the conditions of the impurityimplantation may include, for example, an impurity of As, anacceleration energy of 40 KeV, and an impurity concentration of 1×10¹⁵cm⁻².

Further, annealing is performed, for example, in a N₂ atmosphere at 950°C. for about 10 seconds to activate the impurity.

Thereafter, the inter-layer insulating film 19 and the metal plug 21 areformed similarly to those of the first example, and the nonvolatilesemiconductor memory device 113 illustrated in FIG. 6A can beconstructed.

The nonvolatile semiconductor memory device 113 provides effects such asthose recited below.

In the nonvolatile semiconductor memory device 113, the SiN film of thebarrier insulating film 67 is formed with a thin film thickness withoutcompletely filling the memory string hole Ht. The barrier insulatingfilm 67 prevents the phosphorous-doped polysilicon film 18 f fromdirectly contacting the semiconductor pillar film SPf. The height of theupper end of the barrier insulating film 67 is determined by therecessed depth of the resist, i.e., the coated sacrificial film 69.Unlike films grown by CVD, voids and seams generally do not occur easilyduring filling in the case of a coated film. Therefore, using the coatedsacrificial film 69 makes it difficult for voids to occur in the centerof the memory string hole during the step of recessing in the case wherethe downscaling of memory progresses; and the height of the upper end 69u of the coated sacrificial film 69 can be recessed with goodcontrollability in the next step. Thereby, the controllability of theion implantation step can be improved and the barrier insulating film 67can be reliably left in the semiconductor pillar. Therefore, thephosphorous-doped polysilicon film 18 f no longer contacts thesemiconductor pillar of the memory transistor portion, and thetransistor characteristics also can be improved.

Although ion implantation such as that recited above may be used in thestep described in regard to FIG. 7A, impurity vapor phase diffusion, forexample, may be performed instead of the ion implantation after removingthe coated sacrificial film 69.

Although in this example the same material is used as the secondconducting layer 70 and the first conducting layer 18 and highlyreliable reading operations can be realized while reducing the number ofsteps because the depth of the connection portion CP is made shallowsuch that the second conducting layer 70 does not pass through theconnection portion CP in the horizontal direction, in the case of astructure in which the depth of the connection portion CP is deep andanother material is filled into the space on the inner side of thebarrier insulating film 67, such a material may be insulative unlike thefirst conducting layer 18 to prevent conduction through the connectionportion CP in the horizontal direction.

Thus, in the nonvolatile semiconductor memory device 113, the first coreunit includes the first barrier insulating film provided on the sidewall of the first semiconductor pillar SP1 and the second conductinglayer of the first semiconductor pillar SP1 filled onto the inner sideof the first barrier insulating film to connect to the first conductinglayer of the first semiconductor pillar SP1; and the second core unitincludes the second barrier insulating film provided on the side wall ofthe second semiconductor pillar SP2 and the second conducting layer ofthe second semiconductor pillar SP2 filled onto the inner side of thesecond barrier insulating film to connect to the first conducting layerof the second semiconductor pillar SP2. The first barrier insulatingfilm and the second barrier insulating film are aligned in the interiorof the connection portion CP and connected to each other in theconnection portion CP. The second conducting layer of the firstsemiconductor pillar SP1 and the second conducting layer of the secondsemiconductor pillar SP2 are substantially not provided in the interiorof the connection portion CP.

Fourth Example

FIGS. 8A to 8D are schematic cross-sectional views illustrating theconfiguration of a nonvolatile semiconductor memory device and a methodfor manufacturing the same according to a fourth example of theinvention.

Namely, FIG. 8A is a schematic cross-sectional view illustrating theconfiguration of the nonvolatile semiconductor memory device. FIGS. 8B,8C, and 8D are schematic cross-sectional views in order of the steps,illustrating the method for manufacturing the same.

As illustrated in FIG. 8A, an oxygenated amorphous silicon film 71 isused as the core unit 68 instead of SiN in a nonvolatile semiconductormemory device 114 of the fourth example according to the firstembodiment of the invention. Thereby, the position of the upper end ofthe core unit 68 can be controlled with high precision. In this specificexample, the height of the upper end of the semiconductor pillar SPsubstantially equals to the height of the upper end of the core unit 68.Accordingly, the first conducting layer 18 is provided on the core unit68 (in the Z-axis direction) where the first conducting layer 18 isprovided on the semiconductor pillar SP (in the Z-axis direction).

Such a nonvolatile semiconductor memory device 114 can be manufactured,for example, as follows.

First, the processing illustrated in FIGS. 3A to 3C are implemented toform the memory unit stacked film 61 and the semiconductor pillar filmSPf on the inner wall face of the memory string hole Ht.

Subsequently, as illustrated in FIG. 8B, annealing is performed, forexample, at 600° C. in an inert atmosphere (e.g., in N₂) to increase thecrystallinity of the semiconductor pillar film SPf. Subsequently,annealing is performed in an oxidation atmosphere to oxidize the sideface of the inner side of the semiconductor pillar film SPf. Then, thebarrier insulating film 67 is deposited on the inner side of thesemiconductor pillar film SPf, and the oxygenated amorphous silicon film71 is filled into the interior thereof.

Then, as illustrated in FIG. 8C, the semiconductor pillar film SPf andthe oxygenated amorphous silicon film 71 are recessed by performingetch-back on the oxygenated amorphous silicon film 71 by RIE similarlyto the first example such that an upper end 71 u of the oxygenatedamorphous silicon film 71 is on the upper side of the upper end SGfu ofthe selection gate electrode film SGf by a distance of about 100 nm.Specifically, a distance t1 between the upper end 68 fu of the core unitinsulating film 68 f and the upper end SGfu of the selection gateelectrode film SGf in the Z-axis direction is about 100 nm.

Continuing as illustrated in FIG. 8D, impurity implantation is performedon the semiconductor pillar film SPf similarly to the first example toform the source-drain diffusion region SDR.

Subsequently, the phosphorous-doped polysilicon film 18 f, theinter-layer insulating film 19, and the metal plug 21 are formedsimilarly to those of the first example, and the nonvolatilesemiconductor memory device 114 illustrated in FIG. 8A can beconstructed.

The nonvolatile semiconductor memory device 114 provides effects such asthose recited below.

The nonvolatile semiconductor memory device 114 differs from thenonvolatile semiconductor memory device 111 in that the oxygenatedamorphous silicon film 71 is used instead of SiN as the core unit 68.Therefore, the oxygenated amorphous silicon film 71 and thesemiconductor pillar film SPf are etched at substantially the sameetching rate when recessing the oxygenated amorphous silicon film 71illustrated in FIG. 8C. Thereby, the upper end 71 u of the oxygenatedamorphous silicon film 71 and the upper end of the semiconductor pillarfilm SPf can be formed at substantially the same height after recessing.

In other words, the upper end of the semiconductor pillar film SPf canbe set at the prescribed height (i.e., in this case, proximal to theupper side of the upper end of the selection gate electrode SG) duringthe impurity implantation into the semiconductor pillar film SPf, andthe height of the upper end of the core unit 68 can be set substantiallyto the same height. Thereby, the efficiency of implanting during theimpurity implantation increases, and a low-cost semiconductor devicewith stable operations can be realized.

Fifth Example

FIGS. 9A to 9C are schematic cross-sectional views illustrating theconfiguration of a nonvolatile semiconductor memory device and a methodfor manufacturing the same according to a fifth example of theinvention.

Namely, FIG. 9A is a schematic cross-sectional view illustrating theconfiguration of the nonvolatile semiconductor memory device. FIGS. 9Band 9C are schematic cross-sectional views in order of the steps,illustrating the method for manufacturing the same.

FIGS. 10A to 10C are schematic cross-sectional views in order of thesteps, continuing from FIG. 9C.

As illustrated in FIG. 9A, the diameter of the semiconductor pillar SPof a nonvolatile semiconductor memory device 115 of the fifth exampleaccording to the first embodiment of the invention is larger for theportion piercing the insulating layer 16 than for the portion piercingthe stacked structural unit ML and the selection gate electrode SG.

In other words, the diameter of the semiconductor pillar SP opposing tothe upper end of the insulating layer 16 is larger than the diameter ofthe semiconductor pillar SP opposing to the selection gate electrode SG.By such a structure, a portion of the semiconductor pillar SP proximalto the upper end of the portion opposing to the selection gate electrodeSG is exposed during the impurity implantation into the semiconductorpillar film SPf, and the efficiency of the impurity implantation can beincreased.

Such a nonvolatile semiconductor memory device 115 can be manufactured,for example, as follows.

First, as illustrated in FIG. 9B, the memory transistor hole Hm is madein the stacked structural unit ML and a portion of the back gate BG toalign in the Z-axis direction. The sacrificial film SF made of, forexample, a SiN film is filled into the interior of the memory transistorhole Hm. Thereupon, the inter-layer insulating film 15, the selectiongate electrode film SGf, and the extension inter-layer insulating film16 f are stacked. An opening 16 o is made in the extension inter-layerinsulating film 16 f by lithography and RIE.

Then, a sacrificial film is deposited on the inner side of the opening16 o and the sacrificial film is etched by RIE to form a spacersacrificial film 16 s on the side wall of the opening 160. A boron-dopedsilicate glass film, for example, may be used as the spacer sacrificialfilm 16 s. The spacer sacrificial film 16 s may have a thickness of, forexample, 10 nm.

Continuing as illustrated in FIG. 9C, the selection transistor hole Hsis made, for example, by RIE to pierce the selection gate electrode filmSGf to reach the sacrificial film SF.

Then, as illustrated in FIG. 10A, the spacer sacrificial film 16 s isremoved, for example, in a hydrofluoric acid vapor at 70° C.

Subsequently, the memory string hole Ht having a U-shaped configurationis made similarly to the steps described in regard to FIGS. 3B to 3D andFIG. 4A. The memory unit stacked film 61 is formed on the inner wallface of the memory string hole Ht. The core unit insulating film 68 f isfilled into the interior thereof, and etch-back is performed on the coreunit insulating film 68 f. In other words, the upper end 68 fu of thecore unit insulating film 68 f is positioned about 100 nm on the upperside of the upper end SGfu of the selection gate electrode film SGf.

Then, as illustrated in FIG. 10B, channel impurity implantation isperformed to adjust the threshold of the selection transistor, andsource-drain diffusion layer impurity implantation also is performed.The conditions of the channel impurity implantation may include, forexample, boron as the impurity, an acceleration energy of 60 KeV, and animpurity concentration of 3×10¹⁴ cm⁻². On the other hand, the conditionsof the source-drain diffusion layer impurity implantation may include,for example, phosphorus as the impurity, an acceleration energy of 60KeV, and an impurity concentration of 1×10¹⁵ cm⁻². Thus, the impurityconcentration of the channel is adjusted and the source-drain diffusionregion SDR is formed.

Continuing as illustrated in FIG. 10C, the phosphorous-doped polysiliconfilm 18 f is filled onto the core unit insulating film 68 f in theselection transistor hole Hs. Subsequently, the polysilicon film (thesemiconductor pillar film SPf) is removed from the extension inter-layerinsulating film 16 f.

Subsequently, the inter-layer insulating film 19 and the metal plug 21are formed similarly to those of the first example, and the nonvolatilesemiconductor memory device 115 illustrated in FIG. 9A can beconstructed.

The nonvolatile semiconductor memory device 115 provides effects such asthose recited below.

By implementing the steps illustrated in FIG. 9B, FIG. 9C, and FIG. 10Aand by using the spacer sacrificial film 16 s, the diameter of anextension inter-layer insulating film hole H16 piercing the extensioninter-layer insulating film 16 f is larger than the diameter of theselection transistor hole Hs piercing the selection gate electrode SG.Thereby, the semiconductor pillar film SPf proximal to the selectiongate electrode SG is exposed upward as viewed from above in the Z-axisdirection in the step illustrated in FIG. 10B; and during the impurityimplantation having a perpendicular incidence, the impurity can beimplanted into the semiconductor pillar film SPf directly instead of byrecoiling in the horizontal direction.

Thereby, the nonvolatile semiconductor memory device 115 provides theeffect of drastically increasing the efficiency of the impurityimplantation compared to the nonvolatile semiconductor memory device111, and the effects of reducing the process time for the impurityimplantation and reducing costs are provided. The effect provided by thenonvolatile semiconductor memory device 115 over the nonvolatilesemiconductor memory device 111 in regard to increasing the efficiencyof the impurity implantation is estimated to be at least by a factor often.

Also, it is possible to implant the impurity into the channel portion asrecited above in the step illustrated in FIG. 10B. In other words,although the impurity implantation to the channel portion which is in aportion deeper than the source-drain diffusion region SDR requiresimplantation technology with a higher rate and higher current, theefficiency can be increased by implanting the impurity directly into thechannel portion instead of by recoiling as recited above, and it ispossible to introduce the impurity into the channel portion to adjustthe threshold.

While it is conceivable to use a phosphorus-doped polysilicon film asthe semiconductor pillar film SPf to increase the signal magnitude fromthe memory string (i.e., to increase the cell current), in such a caseas well, it is desirable to maintain the threshold of the selectiontransistor in a positive range to reduce the circuit surface area asmuch as possible. According to the nonvolatile semiconductor memorydevice 115 according to this example, it is possible to increase thecell current while suppressing the increase of the circuit surface areaby performing a compensation implantation of boron into the channelportion, and a low-cost semiconductor device having stable operationscan be realized.

Sixth Example

FIG. 11 is a schematic cross-sectional view illustrating theconfiguration of a nonvolatile semiconductor memory device according toa sixth example of the invention.

As illustrated in FIG. 11, a nonvolatile semiconductor memory device 116of the sixth example according to the first embodiment of the inventionis similar to the nonvolatile semiconductor memory device 115 in thatthe diameter of the extension inter-layer insulating film hole H16piercing the extension inter-layer insulating film 16 f is larger thanthe diameter of the selection transistor hole Hs piercing the selectiongate electrode SG. In other words, the diameter of the semiconductorpillar SP opposing to the upper end of the insulating layer 16 is largerthan the diameter of the semiconductor pillar SP opposing to theselection gate electrode SG. The oxygenated amorphous silicon film 71described in regard to the fourth example is used as the core unit 68.

Thereby, the sixth example provides both the effects described in regardto the fifth example and the effects described in regard to the fourthexample.

FIG. 12 is a schematic perspective view illustrating the configurationof another nonvolatile semiconductor memory device according to thefirst embodiment of the invention.

In FIG. 12 as well, only the electrically conducting portions areillustrated, and the insulating portions are omitted.

As illustrated in FIG. 12, another nonvolatile semiconductor memorydevice 120 according to this embodiment also includes the semiconductorpillars SP piercing the stacked structural unit ML in the Z-axisdirection is provided, where the stacked structural unit ML includes theelectrode films WL stacked with the insulating films 14 (notillustrated).

In such a case, each of the semiconductor pillars SP is independent. Asource-side selection gate electrode SGS is provided on the substrate 11side of the semiconductor pillar SP. A drain-side selection gateelectrode SGD is provided on the side of the semiconductor pillar SPabove the stacked structural unit ML. Each of the source-side selectiongate electrode SGS and the drain-side selection gate electrode SGD is,for example, divided along the Y-axis direction to be aligned in theX-axis direction. Each of the semiconductor pillars SP is selected bythese two selection gates.

In such a case, the electrode films WL may be continuous in the XY planeand need not be separated into an inter digital electrode structure asin the nonvolatile semiconductor memory device 110 described above.

The nonvolatile semiconductor memory device 120 having such a structuremay include the configuration including the drain-side selection gateelectrode SGD of the upper side and the insulating layer 16 providedthereupon from any of the configurations described in regard to theexamples recited above or any combination of such configurations withinthe extent of technical feasibility.

Second Embodiment

FIG. 13 is a flowchart illustrating a method for manufacturing anonvolatile semiconductor memory device according to a second embodimentof the invention.

As illustrated in FIG. 13, in the method for manufacturing thenonvolatile semiconductor memory device according to this embodiment,first, the stacked structural unit ML including the insulating films 14alternately stacked with the electrode films WL is formed on the majorsurface 11 a of the substrate 11 (step S110). Then, the selection gateelectrode film SGf is formed on the stacked structural unit ML (stepS120). Then, the insulating layer 16 is formed on the selection gateelectrode SG (step S130).

Continuing, the first through-hole (the selection transistor hole Hs orthe memory string hole Ht) piercing at least the selection gateelectrode SG and the insulating layer 16 in the first direction (theZ-axis direction) perpendicular to the major surface 11 a is made, and asemiconductor film (the semiconductor pillar film SPf) is formed on theinner side face of the first through-hole (step S140).

Then, the core unit 68 is formed on the inner side of the semiconductorfilm (step S150). Then, the core unit 68 is recessed (step S160).

In step S110 to step S160 recited above, for example, the processingdescribed in regard to FIG. 3A to FIG. 4A is performed.

Then, an impurity is introduced into the semiconductor film (step S170).

In other words, for example, the impurity implantation described inregard to FIG. 4B, the diffusing described in regard to FIG. 5C, etc.,are implemented.

In this manufacturing method, the distance to the selection gateelectrode SG during the impurity implantation is reduced by recessingthe core unit 68; the impurity can be implanted with a highconcentration; and the controllability of the impurity concentration ishigh. Methods that introduce the impurity by diffusing can furthersimplify the steps.

This manufacturing method may be applied to a hollow cylindricalsemiconductor pillar to provide a method for manufacturing thenonvolatile semiconductor memory device that realizes ahigh-concentration source-drain diffusion layer having high positioncontrollability with low manufacturing costs.

FIG. 14 is a flowchart illustrating another method for manufacturing thenonvolatile semiconductor memory device according to the secondembodiment of the invention.

As illustrated in FIG. 14, in another method for manufacturing thenonvolatile semiconductor memory device according to this embodiment,first, the stacked structural unit ML including the insulating films 14alternately stacked with the electrode films WL is formed on the majorsurface 11 a of the substrate 11 (step S110).

Then, the selection gate electrode SG is formed on the stackedstructural unit ML (step S120). Then, the insulating layer 16 is formedon the selection gate electrode SG (step S130).

In step S110 to step S160 recited above, for example, a portion of theprocessing described in regard to FIG. 3A is performed.

Then, the second through-hole (the selection transistor hole Hs)piercing the selection gate electrode SG in the first directionperpendicular to the major surface 11 a is made; and the thirdthrough-hole (the extension inter-layer insulating film hole H16)piercing the insulating layer 16 in the first direction to communicatewith the second through-hole is made, where the diameter of the thirdthrough-hole at the upper end of the insulating layer 16 is larger thanthat of the second through-hole (step S240).

In other words, for example, the processing described in regard to FIG.9B, FIG. 9C, and FIG. 10A is performed.

Then, a semiconductor film (the semiconductor pillar film SPf) is formedon the inner side faces of the first through-hole and the secondthrough-hole (step S250).

In other words, for example, a portion of the processing described inregard to FIG. 10B is performed.

Continuing, an impurity is implanted into a portion of the semiconductorfilm on the selection gate electrode SG side (step S260).

In other words, for example, another portion of the processing describedin regard to FIG. 10B is performed.

According to this manufacturing method, the semiconductor pillar filmSPf proximal to the selection gate electrode SG is exposed upward; andduring the impurity implantation having a perpendicular incidence, theimpurity can be directly implanted into the semiconductor pillar filmSPf, and the efficiency of the impurity implantation can be drasticallyincreased. Also, it is possible to implant the impurity into the channelportion to adjust the threshold; and by performing, for example, acompensation implantation of boron into the channel portion, the cellcurrent can be increased while suppressing the increase of the circuitsurface area, and stable operations can be realized.

Thus, according to the nonvolatile semiconductor memory device and themethod for manufacturing the same according to the embodiments of theinvention, the source-drain diffusion layer can be stably formed at theend of the selection gate electrode SG provided on the upper portion ofthe memory string even in the case where the hollow semiconductor isused as the memory string portion; and it is possible to simultaneouslyrealize an increase of the erasing speed and an increase of the cellcurrent.

In the specification of the application, “perpendicular” and “parallel”refer to not only strictly perpendicular and strictly parallel but alsoinclude, for example, the fluctuation due to manufacturing steps, etc.It is sufficient to be substantially perpendicular and substantiallyparallel.

Hereinabove, exemplary embodiments of the invention are described withreference to specific examples. However, the invention is not limited tothese specific examples. For example, one skilled in the art mayappropriately select specific configurations of components ofnonvolatile semiconductor memory devices such as substrates, electrodefilms, insulating films, insulating layers, stacked structural units,charge storage layers, through-holes, semiconductor pillars, word lines,bit lines, source lines, inter-layer insulating films, and core unitsfrom known art and similarly practice the invention. Such practice isincluded in the scope of the invention to the extent that similareffects thereto are obtained.

Further, any two or more components of the specific examples may becombined within the extent of technical feasibility; and are included inthe scope of the invention to the extent that the purport of theinvention is included.

Moreover, all nonvolatile semiconductor memory devices and methods formanufacturing nonvolatile semiconductor memory devices practicable by anappropriate design modification by one skilled in the art based on thenonvolatile semiconductor memory devices and the methods formanufacturing nonvolatile semiconductor memory devices described aboveas exemplary embodiments of the invention also are within the scope ofthe invention to the extent that the purport of the invention isincluded.

Furthermore, various modifications and alterations within the spirit ofthe invention will be readily apparent to those skilled in the art. Allsuch modifications and alterations should therefore be seen as withinthe scope of the invention. For example, additions, deletions, or designmodifications of components or additions, omissions, or conditionmodifications of steps appropriately made by one skilled in the art inregard to the embodiments described above are within the scope of theinvention to the extent that the purport of the invention is included.

The invention claimed is:
 1. A nonvolatile semiconductor memory device,comprising: a stacked structural unit including a plurality of electrodefilms stacked in a first direction; a first selection gate electrodestacked above the stacked structural unit in the first direction; afirst pillar including a first semiconductor pillar, a first insulatinglayer, and a second insulating layer, at least a part of the firstpillar extending in the stacked structural unit and the first selectiongate electrode in the first direction, the second insulating layer beinglocated between the first insulating layer and the first selection gateelectrode, the first semiconductor pillar being located between thefirst insulating layer and the second insulating layer; a conductivelayer provided on the first semiconductor pillar and the firstinsulating layer; a bit line extending in a second direction, the seconddirection crossing the first direction; and a contact plug providedbetween the conductive layer and the bit line and electrically connectedwith the conductive layer and the bit line, a width of the contact plugin the second direction being larger than a width of the conductivelayer in the second direction.
 2. The device according to claim 1,wherein the width of the contact plug is larger than a width of thefirst pillar in the second direction.
 3. The device according to claim1, wherein the conductive layer includes a semiconductor layercontaining a impurity.
 4. The device according to claim 3, wherein theimpurity includes phosphorous.
 5. The device according to claim 1,wherein the conductive layer includes polysilicon containing a impurity.6. The device according to claim 1, wherein an upper end of the firstinsulating layer in the first direction is located above a position ofan upper end of the first selection gate electrode in the firstdirection.
 7. The device according to claim 1, wherein: the secondinsulating layer is further located between the first insulating layerand the electrode films, at least a part of the second insulating layerincludes: a charge storage layer provided between the firstsemiconductor pillar and the electrode films; a first memory unitinsulating film provided between the electrode films and the chargestorage layer; and a second memory unit insulating film provided betweenthe first semiconductor pillar and the charge storage layer.